format_gsm.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2005, Digium, Inc.
 *
 * Mark Spencer <[email protected]>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief Save to raw, headerless GSM data.
 * \arg File name extension: gsm
 * \ingroup formats
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/mod_format.h"
#include "asterisk/module.h"
#include "asterisk/endian.h"
#include "asterisk/format_cache.h"

#include "msgsm.h"

/* Some Ideas for this code came from makegsme.c by Jeffrey Chilton */

/* Portions of the conversion code are by [email protected] */

#define  GSM_FRAME_SIZE 33
#define  GSM_SAMPLES 160

/* silent gsm frame */
/* begin binary data: */
static const char gsm_silence[] = /* 33 */
{0xD8,0x20,0xA2,0xE1,0x5A,0x50,0x00,0x49,0x24,0x92,0x49,0x24,0x50,0x00,0x49
,0x24,0x92,0x49,0x24,0x50,0x00,0x49,0x24,0x92,0x49,0x24,0x50,0x00,0x49,0x24
,0x92,0x49,0x24};
/* end binary data. size = 33 bytes */

static struct ast_frame *gsm_read(struct ast_filestream *s, int *whennext)
{
   size_t res;

   AST_FRAME_SET_BUFFER(&(s->fr), s->buf, AST_FRIENDLY_OFFSET, GSM_FRAME_SIZE);
   if ((res = fread(s->fr.data.ptr, 1, GSM_FRAME_SIZE, s->f)) != GSM_FRAME_SIZE) {
      if (res) {
         ast_log(LOG_WARNING, "Short read of %s data (expected %d bytes, read %zu): %s\n",
               ast_format_get_name(s->fr.subclass.format), GSM_FRAME_SIZE, res,
               strerror(errno));
      }
      return NULL;
   }
   *whennext = s->fr.samples = GSM_SAMPLES;
   return &s->fr;
}

static int gsm_write(struct ast_filestream *fs, struct ast_frame *f)
{
   int res;
   unsigned char gsm[2*GSM_FRAME_SIZE];

   if (!(f->datalen % 65)) {
      /* This is in MSGSM format, need to be converted */
      int len=0;
      while(len < f->datalen) {
         conv65(f->data.ptr + len, gsm);
         if ((res = fwrite(gsm, 1, 2*GSM_FRAME_SIZE, fs->f)) != 2*GSM_FRAME_SIZE) {
            ast_log(LOG_WARNING, "Bad write (%d/66): %s\n", res, strerror(errno));
            return -1;
         }
         len += 65;
      }
   } else {
      if (f->datalen % GSM_FRAME_SIZE) {
         ast_log(LOG_WARNING, "Invalid data length, %d, should be multiple of 33\n", f->datalen);
         return -1;
      }
      if ((res = fwrite(f->data.ptr, 1, f->datalen, fs->f)) != f->datalen) {
            ast_log(LOG_WARNING, "Bad write (%d/33): %s\n", res, strerror(errno));
            return -1;
      }
   }
   return 0;
}

static int gsm_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
{
   off_t offset = 0, min = 0, cur, max, distance;

   if ((cur = ftello(fs->f)) < 0) {
      ast_log(AST_LOG_WARNING, "Unable to determine current position in g719 filestream %p: %s\n", fs, strerror(errno));
      return -1;
   }

   if (fseeko(fs->f, 0, SEEK_END) < 0) {
      ast_log(AST_LOG_WARNING, "Unable to seek to end of g719 filestream %p: %s\n", fs, strerror(errno));
      return -1;
   }

   if ((max = ftello(fs->f)) < 0) {
      ast_log(AST_LOG_WARNING, "Unable to determine max position in g719 filestream %p: %s\n", fs, strerror(errno));
      return -1;
   }

   /* have to fudge to frame here, so not fully to sample */
   distance = (sample_offset / GSM_SAMPLES) * GSM_FRAME_SIZE;
   if (whence == SEEK_SET) {
      offset = distance;
   } else if (whence == SEEK_CUR || whence == SEEK_FORCECUR) {
      offset = distance + cur;
   } else if (whence == SEEK_END) {
      offset = max - distance;
   }

   /* Always protect against seeking past the begining. */
   offset = (offset < min)?min:offset;
   if (whence != SEEK_FORCECUR) {
      offset = (offset > max)?max:offset;
   } else if (offset > max) {
      int i;
      fseeko(fs->f, 0, SEEK_END);
      for (i=0; i< (offset - max) / GSM_FRAME_SIZE; i++) {
         if (fwrite(gsm_silence, 1, GSM_FRAME_SIZE, fs->f) != GSM_FRAME_SIZE) {
            ast_log(LOG_WARNING, "fwrite() failed: %s\n", strerror(errno));
         }
      }
   }
   return fseeko(fs->f, offset, SEEK_SET);
}

static int gsm_trunc(struct ast_filestream *fs)
{
   int fd;
   off_t cur;

   if ((fd = fileno(fs->f)) < 0) {
      ast_log(AST_LOG_WARNING, "Unable to determine file descriptor for gsm filestream %p: %s\n", fs, strerror(errno));
      return -1;
   }
   if ((cur = ftello(fs->f)) < 0) {
      ast_log(AST_LOG_WARNING, "Unable to determine current position in gsm filestream %p: %s\n", fs, strerror(errno));
      return -1;
   }
   /* Truncate file to current length */
   return ftruncate(fd, cur);
}

static off_t gsm_tell(struct ast_filestream *fs)
{
   off_t offset = ftello(fs->f);

   if (offset < 0) {
      ast_log(AST_LOG_WARNING, "Unable to determine offset for gsm filestream %p: %s\n", fs, strerror(errno));
      return 0;
   }

   return (offset / GSM_FRAME_SIZE) * GSM_SAMPLES;
}

static struct ast_format_def gsm_f = {
   .name = "gsm",
   .exts = "gsm",
   .write = gsm_write,
   .seek =  gsm_seek,
   .trunc = gsm_trunc,
   .tell =  gsm_tell,
   .read =  gsm_read,
   .buf_size = 2*GSM_FRAME_SIZE + AST_FRIENDLY_OFFSET,   /* 2 gsm frames */
};

static int load_module(void)
{
   gsm_f.format = ast_format_gsm;
   if (ast_format_def_register(&gsm_f))
      return AST_MODULE_LOAD_DECLINE;
   return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
   return ast_format_def_unregister(gsm_f.name);
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Raw GSM data",
   .support_level = AST_MODULE_SUPPORT_CORE,
   .load = load_module,
   .unload = unload_module,
   .load_pri = AST_MODPRI_APP_DEPEND
);